Update examples

testsuite/dynload/poly/Makefile

@@ -0,0 +1,4 @@
+TEST=dynload/poly
+EXTRA_OBJS=Plugin.o
+TOP=../../..
+include ../../build.mk

testsuite/dynload/poly/Plugin.hs

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+module Plugin where
+
+import API
+import AltData.Dynamic
+
+my_fun = plugin { 
+                equals = \x y -> (x /= y)  -- a strange equals function :)
+         }
+
+resource_dyn :: Dynamic
+resource_dyn = toDyn my_fun
+

testsuite/dynload/poly/api/API.hs

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+{-# OPTIONS -cpp #-}
+
+module API where
+
+import AltData.Typeable
+
+data Interface = Interface { 
+        equals :: forall t. Eq t => t -> t -> Bool
+     }
+
+--
+-- see how it hides the internal type.. but to compile GHC still checks
+-- the type.
+--
+instance Typeable Interface where
+#if __GLASGOW_HASKELL__ >= 603
+    typeOf i = mkTyConApp (mkTyCon "API.Interface") []
+#else
+    typeOf i = mkAppTy (mkTyCon "API.Interface") []
+#endif
+
+plugin :: Interface
+plugin = Interface  { equals = (==) }
+

testsuite/dynload/poly/prog/Main.hs

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+{-# OPTIONS -cpp #-}
+
+#include "../../../../config.h"
+
+import System.Plugins
+import API
+
+main = do 
+        m_v <- dynload "../Plugin.o" ["../api"]
+                                     [] 
+                                     "resource_dyn"
+        case m_v of
+                LoadFailure _ -> error "didn't compile"
+                LoadSuccess _ (Interface eq) -> do
+                                 putStrLn $ show $   1 `eq` 2
+                                 putStrLn $ show $ 'a' `eq` 'b'
+

testsuite/dynload/poly/prog/expected

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+True
+True